Laser based display method and system

ABSTRACT

The present invention is directed to display technologies. More specifically, various embodiments of the present invention provide projection display systems where one or more laser diodes are used as light source for illustrating images. In one set of embodiments, the present invention provides projector systems that utilize blue and/or green laser fabricated using gallium nitride containing material. In another set of embodiments, the present invention provides projection systems having digital lighting processing engines illuminated by blue and/or green laser devices. In one embodiment, the present invention provides a 3D display system. There are other embodiments as well.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.13/678,122, filed Nov. 15, 2012, which is a division of U.S. applicationSer. No. 12/789,303, filed May 27, 2010, which claims priority to U.S.Provisional Patent Application Nos. 61/182,105, filed May 29, 2009, and61/182,106, filed May 29, 2009, the disclosures of which areincorporated herein by reference in their entirety for all purposes. Thepresent application is also related to U.S. Provisional PatentApplication No. 61/347,800, filed May 24, 2010, entitled “SYSTEM ANDMETHOD OF MULTI-WAVELENGTH LASER APPARATUS,” which is incorporated byreference herein for all purposes. The present application additionallyis related to U.S. Provisional Patent Application No. 61/345,561, filedMay 17, 2010, entitled “METHOD AND SYSTEM FOR PROVIDING DIRECTIONALLIGHT SOURCES WITH BROAD SPECTRUM,” which is incorporated by referenceherein for all purposes. This application is also related to U.S. patentapplication Ser. No. 12/749,466, filed Mar. 29, 2010, which is commonlyassigned and incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention is directed to display technologies. Morespecifically, various embodiments of the present invention provideprojection display systems where one or more laser diodes and/or LEDsare used as light source for illustrating images. In one set ofembodiments, the present invention provides projector systems thatutilize blue and/or green laser fabricated using gallium nitridecontaining material. In another set of embodiments, the presentinvention provides projection systems having digital lighting processingengines illuminated by blue and/or green laser devices. In a specificembodiment, the present invention provides a 3D display system. Thereare other embodiments as well.

Large displays are becoming increasingly popular and are expected togain further traction in the coming years as LCD displays get cheaperfor television and digital advertising becomes more popular at gasstations, malls, and coffee shops. Substantial growth (e.g., over 40%)has been seen in the past several years for large format displays (e.g.,40 inch TVs), and consumers have grown accustomed to larger displays forlaptops and PCs as well. As more viewing content is available via handheld device such as TV, internet and video, displays in handheldconsumer electronics remain small (<3″) with the keyboard, camera, andother features competing for space and power.

Therefore, improved systems for displaying images and/or videos aredesired.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to display technologies. Morespecifically, various embodiments of the present invention provideprojection display systems where one or more laser diodes are used aslight source for illustrating images. In one set of embodiments, thepresent invention provides projector systems that utilize blue and/orgreen laser fabricated using gallium nitride containing material. Inanother set of embodiments, the present invention provides projectionsystems having digital lighting processing engines illuminated by blueand/or green laser devices. There are other embodiments as well.

According to an embodiment, the present invention provides a projectionsystem. The projection system includes an interface for receiving video.The system also includes an image processor for processing the video.The system includes a light source including a plurality of laserdiodes. The plurality of laser diodes includes a blue laser diode. Theblue laser diode is fabricated on non-polar oriented gallium nitridematerial. The system includes a power source electrically coupled to thelight source.

According to another embodiment, the present invention provides aprojection system. The system includes an interface for receiving video.The system also includes an image processor for processing the video.The system includes a light source including a plurality of laserdiodes. The plurality of laser diodes includes a blue laser diode. Theblue laser diode is fabricated on semi-polar oriented gallium nitridematerial. The system also includes a power source electrically coupledto the light source.

According to an embodiment, the present invention provides a projectionapparatus. The projection apparatus includes a housing having anaperture. The apparatus also includes an input interface for receivingone or more frames of images. The apparatus includes a video processingmodule. Additionally, the apparatus includes a laser source. The lasersource includes a blue laser diode, a green laser diode, and a red laserdiode. The blue laser diode is fabricated on a nonpolar or semipolaroriented Ga-containing substrate and has a peak operation wavelength ofabout 430 to 480 nm. The green laser diode is fabricated on a nonpolaror semipolar oriented Ga-containing substrate and has a peak operationwavelength of about 490 nm to 540 nm. The red laser could be fabricatedfrom AlInGaP. The laser source is configured produce a laser beam bycombining outputs from the blue, green, and red laser diodes. Theapparatus also includes a laser driver module coupled to the lasersource. The laser driver module generates three drive currents based ona pixel from the one or more frames of images. Each of the three drivecurrents is adapted to drive a laser diode. The apparatus also includesa microelectromechanical system (MEMS) scanning mirror, or “flyingmirror”, configured to project the laser beam to a specific locationthrough the aperture resulting in a single picture. By rastering thepixel in two dimensions a complete image is formed. The apparatusincludes an optical member provided within proximity of the lasersource, the optical member being adapted to direct the laser beam to theMEMS scanning mirror. The apparatus includes a power source electricallycoupled to the laser source and the MEMS scanning mirror.

According to an embodiment, the present invention provides a projectionapparatus. The projection apparatus includes a housing having anaperture. The apparatus also includes an input interface for receivingone or more frames of images. The apparatus includes a video processingmodule. Additionally, the apparatus includes a laser source. The lasersource includes a blue laser diode, a green laser diode, and a red laserdiode. The blue laser diode is fabricated on a nonpolar or semipolaroriented Ga-containing substrate and has a peak operation wavelength ofabout 430 to 480 nm. The green laser diode is fabricated on a nonpolaror semipolar oriented Ga-containing substrate and has a peak operationwavelength of about 490 nm to 540 nm. In this embodiment, the blue andthe green laser diode would share the same substrate. The red lasercould be fabricated from AlInGaP. The laser source is configured producea laser beam by combining outputs from the blue, green, and red laserdiodes. The apparatus also includes a laser driver module coupled to thelaser source. The laser driver module generates three drive currentsbased on a pixel from the one or more frames of images. Each of thethree drive currents is adapted to drive a laser diode. The apparatusalso includes a MEMS scanning mirror, or “flying mirror”, configured toproject the laser beam to a specific location through the apertureresulting in a single picture. By rastering the pixel in two dimensionsa complete image is formed. The apparatus includes an optical memberprovided within proximity of the laser source, the optical member beingadapted to direct the laser beam to the MEMS scanning mirror. Theapparatus includes a power source electrically coupled to the lasersource and the MEMS scanning mirror.

According to an embodiment, the present invention provides a projectionapparatus. The projection apparatus includes a housing having anaperture. The apparatus also includes an input interface for receivingone or more frames of images. The apparatus includes a video processingmodule. Additionally, the apparatus includes a laser source. The lasersource includes a blue laser diode, a green laser diode, and a red laserdiode. The blue laser diode is fabricated on a nonpolar or semipolaroriented Ga-containing substrate and has a peak operation wavelength ofabout 430 to 480 nm. The green laser diode is fabricated on a nonpolaror semipolar oriented Ga-containing substrate and has a peak operationwavelength of about 490 nm to 540 nm. The red laser could be fabricatedfrom AlInGaP. In this embodiment, two or more of the different colorlasers would be packaged together in the same enclosure. In thiscopackaging embodiment, the outputs from the blue, green, and red laserdiodes would be combined into a single beam. The apparatus also includesa laser driver module coupled to the laser source. The laser drivermodule generates three drive currents based on a pixel from the one ormore frames of images. Each of the three drive currents is adapted todrive a laser diode. The apparatus also includes amicroelectromechanical system (MEMS) scanning mirror, or “flyingmirror”, configured to project the laser beam to a specific locationthrough the aperture resulting in a single picture. By rastering thepixel in two dimensions a complete image is formed. The apparatusincludes an optical member provided within proximity of the lasersource, the optical member being adapted to direct the laser beam to theMEMS scanning mirror. The apparatus includes a power source electricallycoupled to the laser source and the MEMS scanning mirror.

According to another embodiment, the present invention provides aprojection apparatus. The apparatus includes a housing having anaperture. The apparatus includes an input interface for receiving one ormore frames of images. The apparatus includes a laser source. The lasersource includes a blue laser diode, a green laser diode, and a red laserdiode. The blue laser diode is fabricated on a nonpolar or semipolaroriented Ga-containing substrate and has a peak operation wavelength ofabout 430 to 480 nm. The green laser diode is fabricated on a nonpolaror semipolar oriented Ga-containing substrate and has a peak operationwavelength of about 490 nm to 540 nm. The red laser could be fabricatedfrom AlInGaP. The laser source is configured produce a laser beam bycombining outputs from the blue, green, and red laser diodes. Theapparatus includes a digital light processing (DLP) chip comprising adigital mirror device. The digital mirror device including a pluralityof mirrors, each of the mirrors corresponding to one or more pixels ofthe one or more frames of images. The apparatus includes a power sourceelectrically coupled to the laser source and the digital lightprocessing chip. Many variations of this embodiment could exist, such asan embodiment where the green and blue laser diode share the samesubstrate or two or more of the different color lasers could housed inthe same packaged. In this copackaging embodiment, the outputs from theblue, green, and red laser diodes would be combined into a single beam.

According to another embodiment, the present invention provides aprojection apparatus. The apparatus includes a housing having anaperture. The apparatus includes an input interface for receiving one ormore frames of images. The apparatus includes a laser source. The lasersource includes a blue laser diode, a green laser diode, and a red laserdiode. The blue laser diode is fabricated on a nonpolar or semipolaroriented Ga-containing substrate and has a peak operation wavelength ofabout 430 to 480 nm. The green laser diode is fabricated on a nonpolaror semipolar oriented Ga-containing substrate and has a peak operationwavelength of about 490 nm to 540 nm. The red laser could be fabricatedfrom AlInGaP. The apparatus includes a digital light processing chip(DLP) comprising three digital mirror devices. Each of the digitalmirror devices includes a plurality of mirrors. Each of the mirrorscorresponds to one or more pixels of the one or more frames of images.The color beams are respectively projected onto the digital mirrordevices. The apparatus includes a power source electrically coupled tothe laser sources and the digital light processing chip. Many variationsof this embodiment could exist, such as an embodiment where the greenand blue laser diode share the same substrate or two or more of thedifferent color lasers could housed in the same packaged. In thiscopackaging embodiment, the outputs from the blue, green, and red laserdiodes would be combined into a single beam.

As an example, the color wheel may include phosphor material thatmodifies the color of light emitted from the light source. In a specificembodiment, the color wheel includes multiple regions, each of theregions corresponding to a specific color (e.g., red, green, blue,etc.). In an exemplary embodiment, a projector includes a light sourcethat includes blue and red light sources. The color wheel includes aslot for the blue color light and a phosphor containing region forconverting blue light to green light. In operation, the blue lightsource (e.g., blue laser diode or blue LED) provides blue light throughthe slot and excites green light from the phosphor containing region;the red light source provides red light separately. The green light fromthe phosphor may be transmitted through the color wheel, or reflectedback from it. In either case the green light is collected by optics andredirected to the microdisplay. The blue light passed through the slotis also directed to the microdisplay. The blue light source may be alaser diode or LED fabricated on non-polar or semi-polar oriented GaN.Alternatively, a green laser diode may be used, instead of a blue laserdiode with phosphor, to emit green light. It is to be appreciated thatcan be other combinations of colored light sources and color wheelsthereof.

As another example, the color wheel may include multiple phosphormaterials. For example, the color wheel may include both green and redphosphors in combination with a blue light source. In a specificembodiment, the color wheel includes multiple regions, each of theregions corresponding to a specific color (e.g., red, green, blue,etc.). In an exemplary embodiment, a projector includes a light sourcethat includes a blue light source. The color wheel includes a slot forthe blue laser light and two phosphor containing regions for convertingblue light to green light, and blue light and to red light,respectively. In operation, the blue light source (e.g., blue laserdiode or blue LED) provides blue light through the slot and excitesgreen light and red light from the phosphor containing regions. Thegreen and red light from the phosphor may be transmitted through thecolor wheel, or reflected back from it. In either case the green and redlight is collected by optics and redirected to the microdisplay. Theblue light source may be a laser diode or LED fabricated on non-polar orsemi-polar oriented GaN. It is to be appreciated that can be othercombinations of colored light sources and color wheels thereof.

As another example, the color wheel may include blue, green, and redphosphor materials. For example, the color wheel may include blue, greenand red phosphors in combination with a ultra-violet (UV) light source.In a specific embodiment, color wheel includes multiple regions, each ofthe regions corresponding to a specific color (e.g., red, green, blue,etc.). In an exemplary embodiment, a projector includes a light sourcethat includes a UV light source. The color wheel includes three phosphorcontaining regions for converting UV light to blue light, UV light togreen light, and UV light and to red light, respectively. In operation,the color wheel emits blue, green, and red light from the phosphorcontaining regions in sequence. The blue, green and red light from thephosphor may be transmitted through the color wheel, or reflected backfrom it. In either case the blue, green, and red light is collected byoptics and redirected to the microdisplay. The UV light source may be alaser diode or LED fabricated on non-polar or semi-polar oriented GaN.It is to be appreciated that can be other combinations of colored lightsources and color wheels thereof.

According to yet another embodiment, the present invention provides aprojection apparatus. The apparatus includes a housing having anaperture. The apparatus includes an input interface for receiving one ormore frames of images. The apparatus includes a laser source. The lasersource includes a blue laser diode, a green laser diode, and a red laserdiode. The blue laser diode is fabricated on a nonpolar or semipolaroriented Ga-containing substrate and has a peak operation wavelength ofabout 430 to 480 nm. The green laser diode is fabricated on a nonpolaror semipolar oriented Ga-containing substrate and has a peak operationwavelength of about 490 nm to 540 nm. The red laser could be fabricatedfrom AlInGaP. The green laser diode has a wavelength of about 490 nm to540 nm. The laser source is configured produce a laser beam by comingoutputs from the blue, green, and red laser diodes. The apparatusincludes a digital light processing chip comprising three digital mirrordevices. Each of the digital mirror devices includes a plurality ofmirrors. Each of the mirrors corresponds to one or more pixels of theone or more frames of images. The color beams are respectively projectedonto the digital mirror devices. The apparatus includes a power sourceelectrically coupled to the laser sources and the digital lightprocessing chip. Many variations of this embodiment could exist, such asan embodiment where the green and blue laser diode share the samesubstrate or two or more of the different color lasers could housed inthe same packaged. In this copackaging embodiment, the outputs from theblue, green, and red laser diodes would be combined into a single beam.

As an example, the color wheel may include phosphor material thatmodifies the color of light emitted from the light source. In a specificembodiment, the color wheel includes multiple regions, each of theregions corresponding to a specific color (e.g., red, green, blue,etc.). In an exemplary embodiment, a projector includes a light sourcethat includes blue and red light sources. The color wheel includes aslot for the blue color light and a phosphor containing region forconverting blue light to green light. In operation, the blue lightsource (e.g., blue laser diode or blue LED) provides blue light throughthe slot and excites green light from the phosphor containing region;the red light source provides red light separately. The green light fromthe phosphor may be transmitted through the color wheel, or reflectedback from it. In either case the green light is collected by optics andredirected to the microdisplay. The blue light passed through the slotis also directed to the microdisplay. The blue light source may be alaser diode or LED fabricated on non-polar or semi-polar oriented GaN.Alternatively, a green laser diode may be used, instead of a blue laserdiode with phosphor, to emit green light. It is to be appreciated thatcan be other combinations of colored light sources and color wheelsthereof.

As another example, the color wheel may include multiple phosphormaterials. For example, the color wheel may include both green and redphosphors in combination with a blue light source. In a specificembodiment, the color wheel includes multiple regions, each of theregions corresponding to a specific color (e.g., red, green, blue,etc.). In an exemplary embodiment, a projector includes a light sourcethat includes a blue light source. The color wheel includes a slot forthe blue laser light and two phosphor containing regions for convertingblue light to green light, and blue light and to red light,respectively. In operation, the blue light source (e.g., blue laserdiode or blue LED) provides blue light through the slot and excitesgreen light and red light from the phosphor containing regions. Thegreen and red light from the phosphor may be transmitted through thecolor wheel, or reflected back from it. In either case the green and redlight is collected by optics and redirected to the microdisplay. Theblue light source may be a laser diode or LED fabricated on non-polar orsemi-polar oriented GaN. It is to be appreciated that can be othercombinations of colored light sources and color wheels thereof.

As another example, the color wheel may include blue, green, and redphosphor materials. For example, the color wheel may include blue, greenand red phosphors in combination with a ultra-violet (UV) light source.In a specific embodiment, color wheel includes multiple regions, each ofthe regions corresponding to a specific color (e.g., red, green, blue,etc.). In an exemplary embodiment, a projector includes a light sourcethat includes a UV light source. The color wheel includes three phosphorcontaining regions for converting UV light to blue light, UV light togreen light, and UV light and to red light, respectively. In operation,the color wheel emits blue, green, and red light from the phosphorcontaining regions in sequence. The blue, green and red light from thephosphor may be transmitted through the color wheel, or reflected backfrom it. In either case the blue, green, and red light is collected byoptics and redirected to the microdisplay. The UV light source may be alaser diode or LED fabricated on non-polar or semi-polar oriented GaN.It is to be appreciated that can be other combinations of colored lightsources and color wheels thereof.

Various benefits are achieved over pre-existing techniques using thepresent invention. In particular, the present invention enables acost-effective projection systems that utilizes efficient light sources.In a specific embodiment, the light source can be manufactured in arelatively simple and cost effective manner. Depending upon theembodiment, the present apparatus and method can be manufactured usingconventional materials and/or methods according to one of ordinary skillin the art. In one or more embodiments, the laser device is capable ofmultiple wavelengths. Of course, there can be other variations,modifications, and alternatives. Depending upon the embodiment, one ormore of these benefits may be achieved. These and other benefits may bedescribed throughout the present specification and more particularlybelow.

The present invention achieves these benefits and others in the contextof known process technology. However, a further understanding of thenature and advantages of the present invention may be realized byreference to the latter portions of the specification and attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a conventional projection system.

FIG. 2 is a simplified diagram illustrating a projection deviceaccording to an embodiment of the present invention.

FIG. 2A is a detailed cross-sectional view of a laser device 200fabricated on a {20-21} substrate according to an embodiment of thepresent invention.

FIG. 2B is a simplified diagram illustrating a projector having LEDlight sources.

FIG. 3 is an alternative illustration of a projection device accordingto an embodiment of the present invention.

FIG. 3A is a simplified diagram illustrating a laser diodes packagedtogether according to an embodiment of the present invention.

FIG. 3B is a diagram illustrating a cross section of active region withgraded emission wavelength according to an embodiment of the presentinvention.

FIG. 3C is a simplified diagram illustrating a cross section of multipleactive regions according to an embodiment of the present invention.

FIG. 3D is a simplified diagram illustrating a projector having LEDlight sources.

FIG. 4 is a simplified diagram illustrating a projection deviceaccording to an embodiment of the present invention.

FIG. 4A is a simplified diagram illustrating laser diodes integratedinto single package according to an embodiment of the present invention.

FIG. 5 is a simplified diagram of a DLP projection device according toan embodiment of the present invention.

FIG. 5A is a simplified diagram illustrating a DLP projector accordingto an embodiment of the present invention.

FIG. 6 is simplified diagram illustrating a 3-chip DLP projection systemaccording to an embodiment of the present invention.

FIG. 7 is a simplified diagram illustrating 3D display involvingpolarized images filtered by polarized glasses.

FIG. 8 is a simplified diagram illustrating a 3D projection systemaccording to an embodiment of the present invention.

FIG. 9 is a simplified diagram illustrating a LCOS projection system 900according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to display technologies. Morespecifically, various embodiments of the present invention provideprojection display systems where one or more laser diodes are used aslight source for illustrating images. In one set of embodiments, thepresent invention provides projector systems that utilize blue and/orgreen laser fabricated using gallium nitride containing material. Inanother set of embodiments, the present invention provides projectionsystems having digital lighting processing engines illuminated by blueand/or green laser devices. There are other embodiments as well.

As explained above, conventional display type are often inadequate.Miniature projectors address this problem by projecting large images (upto 60 inch and above) from the hand held device, allowing movies,internet surfing and other images to be shared in a size formatconsistent with the displays customers are accustomed to. As a result,pocket projectors, standalone companion pico projectors, and embeddedpico projectors in mobile devices such as phones are becomingincreasingly available.

Present day commercial InGaN-based lasers and LEDs are grown on thepolar c-plane of the GaN crystal. It is well known that InGaN lightemitting layers deposited on this conventional GaN orientation sufferfrom internal polarization-related electric fields. In these structures,spontaneous polarization results from charge asymmetry in the GaNbonding, while piezoelectric polarization is the product of strain. Inquantum well structures, these polarization fields spatially separatethe electron and hole wave functions, reducing their radiativerecombination efficiency. Due to the strain dependence of piezoelectricpolarization, these internal fields grow stronger for withincreased-indium-content in the emitting layers required for blue andespecially for green lasers and LEDs.

In addition to a reduced radiative recombination coefficient to hinderLED brightness, the internal electric fields induce the quantum confinedStark effect (QCSE) within the light emitting quantum well layers. Thiseffect results in a blue-shift of the peak emission wavelength withincreased carrier density in the quantum well layers. Since the carrierdensity is increased with increased current, a blue or green LED willundergo a shift in peak wavelength as a function of current. Suchwavelength dependence on drive current would not be ideal for displayapplications where the LED is subjected to a current modulation schemesince the color will change with current. In a laser diode the carrierdensity is increased with increasing current up until the onset of laserthreshold where the gain overcomes the loss in the cavity. For achievinglasing wavelengths in the blue and green region, such a blue-shift inthe peak wavelength below threshold forces the growth of light emittinglayers with increased indium content to compensate the blue-shift. It iswell-known that such an increase in indium content can result indegraded material quality due to increased strain andindium-segregation. For the realization of highly efficient blue andgreen lasers and LEDs, it is therefore desirable to mitigate orcompletely eliminate polarization-related electric fields.

It has been long understood that growth of device structures onnon-conventional GaN orientations, such as the nonpolar a-plane orm-plane or on semipolar planes between nonpolar planes and the polarc-plane, the polarization fields could be eliminated or mitigated. Onthese novel crystal planes, unique design freedoms became available toboth the epitaxial structure and the device structure. Further, theanisotropic strain of InGaN films grown on nonpolar and semipolarsubstrates results in a reduced effective hole mass, which can increasethe differential gain and reduce the transparency current density inlaser diodes. Devices such as blue and green lasers and LEDs fabricatedon nonpolar and semipolar planes offer exciting potential for improvedperformance with higher radiative recombination efficiency, reduced peakwavelength blue-shift with drive current, increased device designflexibility, and favorable epitaxial growth quality

Typical projectors based on solid-state emitters include:

-   -   a light source (laser or LED),    -   optics,    -   micro-display such as a liquid crystal on silicon (LCOS) or a        digital micro-mirror device (DMD),    -   driver boards, and    -   power source (i.e., battery or power adapter).

Depending on the application, projection systems can utilize polarizedor unpolarized lights. For example, single scanner based projectionsystems (e.g., pico projectors) and DLP based systems typically useunpolarized light source. For certain applications, such as LCOS basedprojection systems, polarized light source is desirable. Usually, blueand green (maybe red) LEDs used in conventional projectors areunpolarized (or demonstrate low polarization ratio), thereby resultingin excessive optical losses from polarization dependent opticalcomponents and exhibit a poor spatial mode quality, which require largeLCOS or LCD chips, and are not viable for compact designs because thelight is not focusable into a small area. Due to the splitting of the Xand Y electronic valence bands on nonpolar and semipolar GaN, the lightemission from devices such as LEDs fabricated on these platforms isinherently polarized. By employing semipolar and/or nonpolar GaN basedLEDs into projection displays using LCOS technologies or otherlight-valves requiring polarized light, the optical losses associatedwith the LEDs would be minimized without having to utilize addedcomponents such as polarization recyclers which increase the complexityand cost of the system. Conventional projection system often use laserand/or LED as light sources to illuminate images. Typically, laser lightsource provides better performance than LED light sources in projectionsystems.

FIG. 1 is a diagram illustrating a conventional projection system. Asshown, blue, green, and red laser lights are combined into a laser beam,which is then projected to an MEMS scanning mirror.

In a conventional projection system such as the one illustrated in FIG.1, a green second-harmonic generation (SHG) laser is used to providegreen laser light. Currently there is no direct diode solution for greenlaser emission, forcing the use of frequency doubled 1060 nm diodelasers which are expensive, bulky, difficult to modulate at high speeds,and emit a narrow spectrum causing speckle in the image. Furthermore,since these devices require generation of a second harmonic usingperiodically-pulsed lithium niobate (PPLN), there are significantinefficiencies associated with the technology.

First there is the efficiency of the 1060 nm device itself. Second thereis the optical coupling losses associated with guiding the light intoand out of the PPLN. Third there is the conversion loss within the PPLN.Finally there is the loss associated with cooling the components to aprecise temperature.

In order to manufacturer highly efficient display that maximize batterylife and minimize cost, size, and weight, optical losses must beminimized from the system. Sources of optical losses in systems include,but are not limited to, losses from optical elements whose transmissionis polarization dependent. In many compact projector such as picoprojectors, a micro-display technology is used which is highlypolarization sensitive, such as LCOS or LCD. A common LCOS baseddisplays typically need highly polarized light sources based on thenature of the liquid crystal display technology.

In various embodiments, the present invention provides blue and greendirect diode GaN based lasers that offers offer highly polarized output,single spatial mode, moderate to large spectral width, high efficiency,and high modulation rates ideal for various types of projection anddisplays, such as pico projectors, DLP projectors, liquid crystal baseddisplays (e.g., liquid crystal on silicon or “LCOS”), and others.

It is to be appreciated that by using highly polarized light source inprojection displays as provided by embodiments of the present invention,the optical efficiency can be maximized with minimal costs and maximumflexibility in the selection on optical components. Conventionalillumination sources such as unpolarized LEDs and systems thereof, wherecomplicated optics are required for polarization recycling to increasethe efficiency from the non-polarized light source. In contrast, byforming blue and green laser and/or LEDs on nonpolar or semipolar GaNthe light output will be highly polarized eliminating the need foradditional optics to deal with polarization.

As described in the present invention, direct diode lasers having GaNbased laser are used for blue and green sources. Conventional c-planeGaN lasers emits unpolarized or near-unpolarized light when laser isbelow threshold. After the laser reaches threshold the output light willbecome polarized with increased current. In contrast, lasers fabricatedon nonpolar or semipolar GaN according to embodiments of the presentinvention emit polarized light below threshold and will also have anincreased polarization ratio with increased current. By using highlypolarized light source in projection displays, the optical efficiencycan be maximized with minimal costs and maximum flexibility in theselection on optical components.

In order to manufacturer a highly efficient displays that maximizebattery life and minimize cost, size, and weight, optical losses must beminimized from the system. For LCOS systems, convention LCOS is oftenshrunk to be as small as possible to fit into a tiny volume and also toreduce cost. Therefore, for maximum optical efficiency and minimal powerconsumption, size, and weight in the display, laser sources are requiredwith high optical spatial brightness.

Conventional LEDs exhibit a poor spatial mode quality, thus requiringlarge LCOS or LCD chips, and are not viable for compact designs becausethe light is not focusable into a small area. In contrast, blue andgreen direct diode GaN based lasers according to the present inventionexhibit a single spatial mode for maximum throughput.

Embodiments of the present invention also provides the benefit ofreduced speckling. For example, frequency doubled 1060 nm diode lasersused in conventional systems produces a narrow spectrum which causesspeckle in the image. Direct diode visible lasers (e.g., green laser)used in embodiments of the present invention offer as much as >100×increase in the spectrum, substantially reducing speckle in the imageand reducing the need for additional expensive and bulky components.

Moreover, frequency doubled 1060 nm diode lasers used in conventionalsystem are inefficient because of the second harmonic generation. Directdiode visible lasers used in the present invention offer the potentialfor substantially higher efficiency with the benefit of reduced opticalcomponents and size and weight of the system.

As explained above, a typical miniature projectors (e.g., picoprojector) includes the following components:

-   -   a light source (laser or LED),    -   optics,    -   micro-display such as a LCOS or a DMD display;    -   driver boards    -   power source, i.e., battery or power adapter

Currently, blue and green (maybe red) LEDs are unpolarized leading toexcessive optical losses and exhibit a poor spatial mode quality, whichrequire large LCOS or LCD chips, and are not viable for compact designsbecause the light is not focusable into a small area. Due to thesplitting of the X and Y electronic valence bands on nonpolar andsemipolar GaN, the light emission from devices such as LEDs fabricatedon these platforms is inherently polarized. By employing semipolarand/or nonpolar GaN based LEDs into projection displays or other LCOStechnologies, the optical losses associated with unpolarized LEDs wouldbe minimized without having to utilize added components such aspolarization recyclers which increase the complexity and cost of thesystem.

Currently there is no direct diode solution for green laser emission,forcing the use of frequency doubled 1060 nm diode lasers which areexpensive, bulky, difficult to modulate at high speeds, and emit anarrow spectrum causing speckle in the image. Furthermore, since thesedevices require generation of a second harmonic usingperiodically-pulsed lithium niobate (PPLN), there are significantinefficiencies associated with the technology. First there is theefficiency of the 1060 nm device itself, second there is the opticalcoupling losses associated with guiding the light into and out of thePPLN, third there is the conversion loss within the PPLN, And finallythere is the loss associated with cooling the components to a precisetemperature.

The blue and green direct diode GaN based lasers according toembodiments of the present invention offers highly polarized output,single spatial mode, moderate to large spectral width, high efficiency,and high modulation rates ideal for liquid crystal based displays.

Conventional approaches for frequency doubling achieves high spatialbrightness, but it does not conveniently enable high modulationfrequencies and produces image artifacts when attempted. This limits themodulation frequency of the source to ˜100 MHz where amplitude (analog)modulation must be utilized. With increased frequency capability to ˜300MHz, pulsed (digital) modulation could be used which would simplify thesystem and eliminate the need for look-up tables.

With a direct diode solution afford by embodiments of the presentinvention, modulation frequencies beyond 300 MHz can be achieved anddigital operation can be realized. Nonpolar and/or semipolar based GaNlasers hold great promise for enabling the direct diode green solution,and therefore, digital scanning micro mirror projectors.

FIG. 2 is a simplified diagram illustrating a projection deviceaccording to an embodiment of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. A projection system 250includes a MEMS scanning mirror 251, a mirror 252, an optical member254, green laser diode 253, red laser diode 256, and blue laser diode255.

As an example, the projection system 250 is a pico projector. Inaddition to the components illustrated in FIG. 2, the projection system250 also includes a housing having an aperture and an input interfacefor receiving one or more frames of images. The projection system 250also includes a video processing module. In one embodiment, the videoprocessing module is electrically coupled to an ASIC for driving thelaser diodes and the MEMS scanning mirrorscanning mirror 251.

In one embodiment, the laser diodes together with the optical member 254form a laser source. The green laser diode 253 is characterized by awavelength of about 490 nm to 540 nm. The laser source is configuredproduce a laser beam by combining outputs from the blue, green, and redlaser diodes. Depending on the application, various types of opticalcomponents may be used to combine the light outputs from the laserdiodes. For example, optical components can be dichroic lenses, prisms,converging lenses, etc. In a specific embodiment, the combined laserbeam is polarized.

In one embodiment, a laser driver module is provided. Among otherthings, the laser driver module is adapted to adjust the amount of powerto be provided to the laser diodes. For example, the laser driver modulegenerates three drive currents based one or more pixels from the one ormore frames of images, each of the three drive currents being adapted todrive a laser diode. In a specific embodiment, the laser driver moduleis configured to generate pulse-modulated signal at a frequency range ofabout 50 to 300 MHz.

The MEMS scanning mirror 251 is configured to project the laser beam toa specific location through the aperture. For example, the MEMS scanningmirror 251 process one pixel at a specific time onto a specific locationcorresponding to an pixel of an image. At a high frequency, pixelsprojected by the MEMS scanning mirror 251 form images.

The MEMS scanning mirror 251 receives light from the laser source thoughmirror 252. As shown, the mirror 252 is provided within proximity of thelaser source. Among other things, the optical member is adapted todirect the laser beam to the MEMS scanning mirror 251.

It is to be appreciated the projection system 250 include othercomponents as well, such as a power source electrically coupled to thelaser source and the MEMS scanning mirror 251. Other components caninclude buffer memory, communication interface, network interface, etc.

As described above, a key component of the projection system 250 is thelaser light source. In contrast to conventional projection systems,embodiments of the present invention use highly efficient laser diodes.In a specific embodiment, the blue laser diode operates in a singlelateral mode. For example, the blue laser diode is characterized by aspectral width of about 0.5 nm to 2 nm. In a specific embodiment, theblue laser diode is designed for integration into portable applicationssuch as embedded and companion pico projectors and features 60 mW of 445nm single mode output power in a compact TO-38 package. For example, theblue lasers operate with high efficiency and require minimal powerconsumption over a broad temperature range, meeting the demandingrequirements of consumer projection displays, defense pointers andilluminators, biomedical instrumentation and therapeutics, andindustrial imaging applications. According to various embodiments, bluelasers are based on the Indium Gallium Nitride (InGaN) semiconductortechnology and are fabricated on GaN substrates.

In various embodiments, the blue and green laser diodes are fabricatedusing GaN material. The blue laser diode may be semi-polar or non-polar.Similarly, the green laser diode can be semi-polar or non-polar. Forexample, the red laser diode can be fabricated using GaAlInP material.For example, following combinations of laser diodes are provided, butthere could be others:

-   -   Blue polar+Green nonpolar+Red*AlInGaP    -   Blue polar+Green semipolar+Red*AlInGaP    -   Blue polar+Green polar+Red*AlInGaP    -   Blue semipolar+Green nonpolar+Red*AlInGaP    -   Blue semipolar+Green semipolar+Red*AlInGaP    -   Blue semipolar+Green polar+Red*AlInGaP    -   Blue nonpolar+Green nonpolar+Red*AlInGaP    -   Blue nonpolar+Green semipolar+Red*AlInGaP    -   Blue nonpolar+Green polar+Red*AlInGaP

As an example, blue and green laser diodes can be manufactured onm-plane. In a specific embodiment, a blue or green laser diode includesa gallium nitride substrate member having the off-cut m-planecrystalline surface region. In a specific embodiment this offcut angleis between −2.0 and −0.5 degrees toward the c-plane. In a specificembodiment, the gallium nitride substrate member is a bulk GaN substratecharacterized by having a semipolar or non-polar crystalline surfaceregion, but can be others. In a specific embodiment, the bulk nitrideGaN substrate comprises nitrogen and has a surface dislocation densitybelow 10⁵ cm⁻². The nitride crystal or wafer may compriseAl_(x)In_(y)Ga_(1-x-y)N, where 0≦x, y, x+y≦1. In one specificembodiment, the nitride crystal comprises GaN, but can be others. In oneor more embodiments, the GaN substrate has threading dislocations, at aconcentration between about 10⁵ cm⁻² and about 10⁸ cm⁻², in a directionthat is substantially orthogonal or oblique with respect to the surface.As a consequence of the orthogonal or oblique orientation of thedislocations, the surface dislocation density is below about 10⁵ cm⁻².In a specific embodiment, the device can be fabricated on a slightlyoff-cut semipolar substrate as described in U.S. patent application Ser.No. 12/749,466, file Mar. 29, 2010, which is commonly assigned andincorporated by reference herein.

In a specific embodiment where the laser is fabricated on the {20-21}semipolar GaN surface orientation, the device has a laser stripe regionformed overlying a portion of the off-cut crystalline orientationsurface region. In a specific embodiment, the laser stripe region ischaracterized by a cavity orientation substantially in a projection of ac-direction, which is substantially normal to the a-direction. In aspecific embodiment, the laser strip region has a first end and a secondend. In a preferred embodiment, the laser cavity is oriented formed in aprojection of the c-direction on a {20-21} gallium and nitrogencontaining substrate having a pair of cleaved mirror structures, at theend of cavity. Of course, there can be other variations, modifications,and alternatives.

In a specific embodiment where the laser is fabricated on the nonpolarm-plane GaN surface orientation, the device has a laser stripe regionformed overlying a portion of the off-cut crystalline orientationsurface region. In a specific embodiment, the laser stripe region ischaracterized by a cavity orientation substantially in the c-direction,which is substantially normal to the a-direction. In a specificembodiment, the laser strip region has a first end and a second end. Ina preferred embodiment, the laser cavity is oriented formed in thec-direction on an m-plane gallium and nitrogen containing substratehaving a pair of cleaved mirror structures, at the end of cavity. Ofcourse, there can be other variations, modifications, and alternatives.

In a preferred embodiment, the device has a first cleaved facet providedon the first end of the laser stripe region and a second cleaved facetprovided on the second end of the laser stripe region. In one or moreembodiments, the first cleaved is substantially parallel with the secondcleaved facet. Mirror surfaces are formed on each of the cleavedsurfaces. The first cleaved facet comprises a first mirror surface. In apreferred embodiment, the first mirror surface is provided by a top-sideskip-scribe scribing and breaking process. The scribing process can useany suitable techniques, such as a diamond scribe or laser scribe orcombinations. In a specific embodiment, the first mirror surfacecomprises a reflective coating. The reflective coating is selected fromsilicon dioxide, hafnia, and titania, tantalum pentoxide, zirconia,including combinations, and the like. Depending upon the embodiment, thefirst mirror surface can also comprise an anti-reflective coating. Ofcourse, there can be other variations, modifications, and alternatives.

Also in a preferred embodiment, the second cleaved facet comprises asecond mirror surface. The second mirror surface is provided by a topside skip-scribe scribing and breaking process according to a specificembodiment. Preferably, the scribing is diamond scribed or laser scribedor the like. In a specific embodiment, the second mirror surfacecomprises a reflective coating, such as silicon dioxide, hafnia, andtitania, tantalum pentoxide, zirconia, combinations, and the like. In aspecific embodiment, the second mirror surface comprises ananti-reflective coating. Of course, there can be other variations,modifications, and alternatives.

In a specific embodiment, the laser stripe has a length and width. Thelength ranges from about 50 microns to about 3000 microns. The stripalso has a width ranging from about 0.5 microns to about 50 microns, butcan be other dimensions. In a specific embodiment, the width issubstantially constant in dimension, although there may be slightvariations. The width and length are often formed using a masking andetching process, which are commonly used in the art.

In a specific embodiment, the present invention provides an alternativedevice structure capable of emitting 501 nm and greater light in a ridgelaser embodiment. The device is provided with one or more of thefollowing epitaxially grown elements, but is not limiting:

an n-GaN cladding layer with a thickness from 100 nm to 5000 nm with Sidoping level of 5E17 to 3E18 cm−3

an n-side SCH layer comprised of InGaN with molar fraction of indium ofbetween 3% and 10% and thickness from 20 to 100 nm

multiple quantum well active region layers comprised of at least two2.0-8.5 nm InGaN quantum wells separated by thin 2.5 nm and greater, andoptionally up to about 8 nm, GaN barriers

a p-side SCH layer comprised of InGaN with molar a fraction of indium ofbetween 1% and 10% and a thickness from 15 nm to 100 nm

an electron blocking layer comprised of AlGaN with molar fraction ofaluminum of between 12% and 22% and thickness from 5 nm to 20 nm anddoped with Mg.

a p-GaN cladding layer with a thickness from 400 nm to 1000 nm with Mgdoping level of 2E17 cm−3 to 2E19 cm−3

a p++-GaN contact layer with a thickness from 20 nm to 40 nm with Mgdoping level of 1E19 cm−3 to 1E21 cm−3

In a specific embodiment, the laser device is fabricated on a {20-21}semipolar Ga-containing substrate. But it is to be understood that thelaser device can be fabricated on other types of substrates such asnonpolar oriented Ga-containing substrate as well.

While light source based on red, green, and blue color sources arewidely used, other combinations are possible as well. According to anembodiment of the present invention, the light source used in aprojection system combines a yellow light source with the red, green,and blue light sources. For example, the addition of yellow lightsources improves the color characteristics (e.g., allowing for widercolor gamut) of RBG based projection and display systems. In a specificembodiment, an RGYB light sources is used for a projection system. Theyellow light source can be a yellow laser diode manufactured fromgallium nitride material or AlInGaP material. In various embodiments,the yellow light source can have a polar, non-polar, or semi-polarorientation. It is to be appreciated that projection systems accordingto the present invention may use light sources in other colors as well.For example, other colors include cyan, magenta, and others. In aspecific embodiment, the laser diodes of the different colors areseparately packaged. In another specific embodiment, the laser diodes oftwo or more of the different colors are copackaged. In yet anotherspecific embodiment, the laser diodes of two or more of the differentcolors are fabricated on the same substrate.

FIG. 2A is a detailed cross-sectional view of a laser device 200fabricated on a {20-21} substrate according to an embodiment of thepresent invention. This diagram is merely an example, which should notunduly limit the scope of the claims herein. One of ordinary skill inthe art would recognize other variations, modifications, andalternatives. As shown, the laser device includes gallium nitridesubstrate 203, which has an underlying n-type metal back contact region201. In a specific embodiment, the metal back contact region is made ofa suitable material such as those noted below and others. Furtherdetails of the contact region can be found throughout the presentspecification and more particularly below.

In a specific embodiment, the device also has an overlying n-typegallium nitride layer 205, an active region 207, and an overlying p-typegallium nitride layer structured as a laser stripe region 209. In aspecific embodiment, each of these regions is formed using at least anepitaxial deposition technique of metal organic chemical vapordeposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxialgrowth techniques suitable for GaN growth. In a specific embodiment, theepitaxial layer is a high quality epitaxial layer overlying the n-typegallium nitride layer. In some embodiments the high quality layer isdoped, for example, with Si or O to form n-type material, with a dopantconcentration between about 10¹⁶ cm⁻³ and 10²⁰ cm⁻³.

In a specific embodiment, an n-type Al_(u)In_(v)Ga_(1-u-v)N layer, where0≦u, v, u+v≦1, is deposited on the substrate. In a specific embodiment,the carrier concentration may lie in the range between about 10¹⁶ cm⁻³and 10²⁰ cm⁻³. The deposition may be performed using MOCVD or MBE. Ofcourse, there can be other variations, modifications, and alternatives.

As an example, the bulk GaN substrate is placed on a susceptor in anMOCVD reactor. After closing, evacuating, and back-filling the reactor(or using a load lock configuration) to atmospheric pressure, thesusceptor is heated to a temperature between about 900 and about 1200degrees Celsius in the presence of a nitrogen-containing gas. In onespecific embodiment, the susceptor is heated to approximately 1100degrees Celsius under flowing ammonia. A flow of a gallium-containingmetalorganic precursor, such as trimethylgallium (TMG) ortriethylgallium (TEG) is initiated, in a carrier gas, at a total ratebetween approximately 1 and 50 standard cubic centimeters per minute(sccm). The carrier gas may comprise hydrogen, helium, nitrogen, orargon. The ratio of the flow rate of the group V precursor (ammonia) tothat of the group III precursor (trimethylgallium, triethylgallium,trimethylindium, trimethylaluminum) during growth is between about 2000and about 12000. A flow of disilane in a carrier gas, with a total flowrate of between about 0.1 and 10 sccm, is initiated.

In a specific embodiment, the laser stripe region is made of the p-typegallium nitride layer 209. In a specific embodiment, the laser stripe isprovided by an etching process selected from dry etching or wet etching.In a preferred embodiment, the etching process is dry, but can beothers. As an example, the dry etching process is an inductively coupledprocess using chlorine bearing species or a reactive ion etching processusing similar chemistries. Again as an example, the chlorine bearingspecies are commonly derived from chlorine gas or the like. The devicealso has an overlying dielectric region, which exposes 213 contactregion. In a specific embodiment, the dielectric region is an oxide suchas silicon dioxide or silicon nitride, but can be others. The contactregion is coupled to an overlying metal layer 215. The overlying metallayer is a multilayered structure containing palladium and gold (Pd/Au),platinum and gold (Pt/Au), nickel gold (Ni/Au), but can be others. Ofcourse, there can be other variations, modifications, and alternatives.

In a specific embodiment, the laser device has active region 207. Theactive region can include one to twenty quantum well regions accordingto one or more embodiments. As an example following deposition of then-type Al_(u)In_(v)Ga_(1-u-v)N layer for a predetermined period of time,so as to achieve a predetermined thickness, an active layer isdeposited. The active layer may be comprised of multiple quantum wells,with 2-10 quantum wells. The quantum wells may be comprised of InGaNwith GaN barrier layers separating them. In other embodiments, the welllayers and barrier layers comprise Al_(w)In_(x)Ga_(1-w-x)N andAl_(y)In_(z)Ga_(1-y-z)N, respectively, where 0≦w, x, y, z, w+x, y+z≦1,where w<u, y and/or x>v, z so that the bandgap of the well layer(s) isless than that of the barrier layer(s) and the n-type layer. The welllayers and barrier layers may each have a thickness between about 1 nmand about 20 nm. The composition and structure of the active layer arechosen to provide light emission at a preselected wavelength. The activelayer may be left undoped (or unintentionally doped) or may be dopedn-type or p-type. Of course, there can be other variations,modifications, and alternatives.

In a specific embodiment, the active region can also include an electronblocking region, and a separate confinement heterostructure. In someembodiments, an electron blocking layer is preferably deposited. Theelectron-blocking layer may comprise Al_(s)In_(t)Ga_(1-s-t)N, where 0≦s,t, s+t≦1, with a higher bandgap than the active layer, and may be dopedp-type. In one specific embodiment, the electron blocking layercomprises AlGaN. In another embodiment, the electron blocking layercomprises an AlGaN/GaN super-lattice structure, comprising alternatinglayers of AlGaN and GaN, each with a thickness between about 0.2 nm andabout 5 nm. In Of course, there can be other variations, modifications,and alternatives.

As noted, the p-type gallium nitride structure is deposited above theelectron blocking layer and active layer(s). The p-type layer may bedoped with Mg, to a level between about 10¹⁶ cm⁻³ and 10²² cm⁻³, and mayhave a thickness between about 5 nm and about 1000 nm. The outermost1-50 nm of the p-type layer may be doped more heavily than the rest ofthe layer, so as to enable an improved electrical contact. In a specificembodiment, the laser stripe is provided by an etching process selectedfrom dry etching or wet etching. In a preferred embodiment, the etchingprocess is dry, but can be others. The device also has an overlyingdielectric region, which exposes 213 contact region. In a specificembodiment, the dielectric region is an oxide such as silicon dioxide,but can be others such as silicon nitride. Of course, there can be othervariations, modifications, and alternatives.

It is to be appreciated the light source of the projector 250 mayinclude one or more LED as well. FIG. 2B is a simplified diagramillustrating a projector having LED light sources. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As an example, the blue andgreen LEDs are manufactured from gallium nitride containing material. Inone specific embodiment, the blue LED is characterized by a non-polarorientation. In another embodiment, the blue LED is characterized by asemi-polar orientation.

FIG. 3 is an alternative illustration of a projection device accordingto an embodiment of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. In FIG. 3, a projection device includes an MEMSscanning mirror, a mirror, a light conversion member, a red laser diode,a blue diode, and green laser diode. The blue and green laser diodes asshown are integrated as a single package. For example, the blue andgreen laser shared the same substrate and surface. Output from the blueand green laser diodes are emitted from a common plane of surface. It isto be appreciated that that by having blue and green laser diodesco-packaged, it is possible to substantially reduce the size and cost(e.g., fewer parts) of the projector device.

In addition, the green and blue laser diodes are characterized by a highefficiency. For example, the blue on the green laser diode aremanufactured from bulk gallium nitride material. The blue laser diodecan be non-polar or semi-polar oriented. The green laser diodessimilarly can be non-polar polar or semipolar. For example, followingcombinations of laser diodes are provided, but there could be others:

-   -   Blue polar+Green nonpolar+Red*AlInGaP    -   Blue polar+Green semipolar+Red*AlInGaP    -   Blue polar+Green polar+Red*AlInGaP    -   Blue semipolar+Green nonpolar+Red*AlInGaP    -   Blue semipolar+Green semipolar+Red*AlInGaP    -   Blue semipolar+Green polar+Red*AlInGaP    -   Blue nonpolar+Green nonpolar+Red*AlInGaP    -   Blue nonpolar+Green semipolar+Red*AlInGaP    -   Blue nonpolar+Green polar+Red*AlInGaP

In one embodiment, the green laser diode is characterized by wavelengthof between 480 nm to 540 nm, which is different from conventionalproduction devices that use an infrared laser diode (i.e., emissionwavelength of about 1060 nm) and use SHG to double the frequency.

FIG. 3A is a simplified diagram illustrating a laser diodes packagedtogether according to an embodiment of the present invention. Thisdiagram is merely an example, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As shown in FIG. 3A, twolaser diodes are provided on a single package. For example, laser 1 asshown in a blue laser diode and laser 2 is a green laser diode. Opticsmay be used to combine the outputs of lasers.

The output of the two laser as shown in FIG. 3A can be combined invarious ways. For example, optical components such as dichroic lens,waveguide, can be used to combine the outputs of the laser 1 and laser 2as shown.

In other embodiments, blue and green laser diodes are monolithicallyintegrated. FIG. 3B is a diagram illustrating a cross section of activeregion with graded emission wavelength according to an embodiment of thepresent invention. This diagram is merely an example, which should notunduly limit the scope of the claims. One of ordinary skill in the artwould recognize many variations, alternatives, and modifications. Asillustrating FIG. 3B, for example, active regions having differentemission gradient are used. Ridged waveguides at different portion ofthe active region are adapted to emit different wavelength. FIG. 3Bshows a cross-section of an active region with graded emissionwavelength including ridge waveguide of laser 301 operating at a firstpeak wavelength determined by the cavity position relative to theemission wavelength of the graded active region 302; ridge waveguide oflaser 303 operating at a second peak wavelength determined by the cavityposition relative to the emission wavelength of the graded active region302; active region 302 with a peak emission gradient; n-type claddingregion 304; and substrate 305. FIG. 3B shows an example of a gradedemission wavelength active region configuration where adjacent lasersare operating at different wavelengths as a result of lasing off beingpositioned in areas where the active region possesses different peakemission wavelengths.

FIG. 3C is a simplified diagram illustrating a cross section of multipleactive regions according to an embodiment of the present invention. Thisdiagram is merely an example, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. Among other things, eachactive region is associated with a specific wavelength. FIG. 3C shows across-section of multiple active regions including a ridge waveguide oflaser 311 operating at a first peak wavelength from active region 312,which overlies active region 312 with a first peak wavelength; ridgewaveguide of laser 313 operating at a second peak wavelength from activeregion 314, which overlies active region 304 with a second peakwavelength; n-type cladding region 315; and substrate 316. FIG. 3C showsan example of a multiple active region configuration where adjacentlasers are operating at different wavelengths as a result of lasing offof two different active regions with different peak wavelengths.

It is to be appreciated the light source of the projector 300 mayinclude one or more LED as well. FIG. 3D is a simplified diagramillustrating a projector having LED light sources. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As an example, the blue andgreen LEDs are manufactured from gallium nitride containing material. Inone specific embodiment, the blue LED is characterized by a non-polarorientation. In another embodiment, the blue LED is characterized by asemi-polar orientation.

FIG. 4 is a simplified diagram illustrating a projection deviceaccording to an embodiment of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As shown in FIG. 4, blue,green, and red laser diodes are integrated into a light source 401. Thelight source 401 is combines outputs of each of the laser diodes. Thecombined light is projected onto the mirror, which reflects the combinedlight onto the MEMS scanning mirror. It is to be appreciated that, byproviding laser diodes in the same package, both the size and cost ofthe light source 401 can be reduced. For example, following combinationsof laser diodes are provided, but there could be others:

-   -   Blue polar+Green nonpolar+Red*AlInGaP    -   Blue polar+Green semipolar+Red*AlInGaP    -   Blue polar+Green polar+Red*AlInGaP    -   Blue semipolar+Green nonpolar+Red*AlInGaP    -   Blue semipolar+Green semipolar+Red*AlInGaP    -   Blue semipolar+Green polar+Red*AlInGaP    -   Blue nonpolar+Green nonpolar+Red*AlInGaP    -   Blue nonpolar+Green semipolar+Red*AlInGaP    -   Blue nonpolar+Green polar+Red*AlInGaP

FIG. 4A is a simplified diagram illustrating laser diodes integratedinto single package according to an embodiment of the present invention.This diagram is merely an example, which should not unduly limit thescope of the claims. One of ordinary skill in the art would recognizemany variations, alternatives, and modifications. For examples, laser 1can be a green laser diode, laser 2 can be a red laser diode, and laser3 can be a blue laser diode. Depending on the application, the greenlaser diode can be fabricated on a semi-polar, non-polar, or polargallium containing substrates. Similarly, the blue laser diode can beformed on semi-polar, non-polar, or polar gallium containing substrates.

It is to be appreciated that various projection systems according to thepresent invention have wide range of applications. In variousembodiments, the projections systems described above are integrated oncellular telephone, camera, personal computer, portable computer, andother electronic devices.

FIG. 5 is a simplified diagram of a DLP projection device according toan embodiment of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. As shown in FIG. 5, a projection apparatus includes,among other things, a light source, a condensing lens, a color wheel, ashaping lens, and a digital lighting processor (DLP) board, and aprojection lens. The DLP board, among other things, includes aprocessor, a memory, and a digital micromirror device (DMD).

As an example, the color wheel may include phosphor material thatmodifies the color of light emitted from the light source. In a specificembodiment, the color wheel includes multiple regions, each of theregions corresponding to a specific color (e.g., red, green, blue,etc.). In an exemplary embodiment, a projector includes a light sourcethat includes blue and red light sources. The color wheel includes aslot for the blue color light and a phosphor containing region forconverting blue light to green light. In operation, the blue lightsource (e.g., blue laser diode or blue LED) provides blue light throughthe slot and excites green light from the phosphor containing region;the red light source provides red light separately. The green light fromthe phosphor may be transmitted through the color wheel, or reflectedback from it. In either case the green light is collected by optics andredirected to the microdisplay. The blue light passed through the slotis also directed to the microdisplay. The blue light source may be alaser diode and/or LED fabricated on non-polar or semi-polar orientedGaN. In some cases, by combining both blue lasers and blue LEDs, thecolor characteristics could be improved. Alternate sources for the greenlight could include green laser diodes and/or green LEDs, which could befabricated from nonpolar or semipolar Ga-containing substrates. In someembodiments, it could be beneficial to include some combination of LEDs,lasers, and or phosphor converted green light. It is to be appreciatedthat can be other combinations of colored light sources and color wheelsthereof.

As another example, the color wheel may include multiple phosphormaterials. For example, the color wheel may include both green and redphosphors in combination with a blue light source. In a specificembodiment, the color wheel includes multiple regions, each of theregions corresponding to a specific color (e.g., red, green, blue,etc.). In an exemplary embodiment, a projector includes a light sourcethat includes a blue light source. The color wheel includes a slot forthe blue laser light and two phosphor containing regions for convertingblue light to green light, and blue light and to red light,respectively. In operation, the blue light source (e.g., blue laserdiode or blue LED) provides blue light through the slot and excitesgreen light and red light from the phosphor containing regions. Thegreen and red light from the phosphor may be transmitted through thecolor wheel, or reflected back from it. In either case the green and redlight is collected by optics and redirected to the microdisplay. Theblue light source may be a laser diode or LED fabricated on non-polar orsemi-polar oriented GaN. It is to be appreciated that can be othercombinations of colored light sources and color wheels thereof.

As another example, the color wheel may include blue, green, and redphosphor materials. For example, the color wheel may include blue, greenand red phosphors in combination with a ultra-violet (UV) light source.In a specific embodiment, color wheel includes multiple regions, each ofthe regions corresponding to a specific color (e.g., red, green, blue,etc.). In an exemplary embodiment, a projector includes a light sourcethat includes a UV light source. The color wheel includes three phosphorcontaining regions for converting UV light to blue light, UV light togreen light, and UV light and to red light, respectively. In operation,the color wheel emits blue, green, and red light from the phosphorcontaining regions in sequence. The blue, green and red light from thephosphor may be transmitted through the color wheel, or reflected backfrom it. In either case the blue, green, and red light is collected byoptics and redirected to the microdisplay. The UV light source may be alaser diode or LED fabricated on non-polar or semi-polar oriented GaN.It is to be appreciated that can be other combinations of colored lightsources and color wheels thereof.

The light source as shown could be made laser-based. In one embodiment,the output from the light source is laser beam characterized by asubstantially white color. In one embodiment, the light source combineslight output from blue, green, and red laser diodes. For example, theblue, green, and red laser diode can be integrated into a single packageas described above. Other combinations are possible as well. Forexample, blue and green laser diodes share a single package while thered laser diode is packaged by itself. In this embodiment the lasers canbe individually modulated so that color is time-sequenced, and thusthere is no need for the color wheel. The blue laser diode can be polar,semipolar, and non-polar. Similarly, green laser diode can be polar,semipolar, and non-polar. For example, blue and/or green diodes aremanufactured from bulk substrate containing gallium nitride material.For example, following combinations of laser diodes are provided, butthere could be others:

-   -   Blue polar+Green nonpolar+Red*AlInGaP    -   Blue polar+Green semipolar+Red*AlInGaP    -   Blue polar+Green polar+Red*AlInGaP    -   Blue semipolar+Green nonpolar+Red*AlInGaP    -   Blue semipolar+Green semipolar+Red*AlInGaP    -   Blue semipolar+Green polar+Red*AlInGaP    -   Blue nonpolar+Green nonpolar+Red*AlInGaP    -   Blue nonpolar+Green semipolar+Red*AlInGaP    -   Blue nonpolar+Green polar+Red*AlInGaP

In FIG. 5, the DLP projection system utilizes a color wheel to projectone color (e.g., red, green, or blue) of light at a time to the DMD. Thecolor wheel is needed because the light source continuously providewhite light. It is to be appreciated that because solid state devicesare used as light source in the embodiments of the present invention, aDLP projector according to the present invention does not require thecolor wheel shown in FIG. 5. FIG. 5A is a simplified diagramillustrating a DLP projector according to an embodiment of the presentinvention. This diagram is merely an example, which should not undulylimit the scope of the claims. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications.

In an alternative embodiment, the light source comprises a single laserdiode. For example, the light source comprises a blue laser diode thatoutputs blue laser beams. The light source also includes one or moreoptical members that changes the blue color of the laser beam. Forexample, the one or more optical members includes phosphor material. Thelaser beam excites the phosphor material to form a substantially whiteemission source which becomes the light source for the projectiondisplay. In this embodiment, a color wheel is needed in order tosequence the blue, green, and red frames to the DLP.

A projection system 500 includes a light source 501, a light sourcecontroller 502, an optical member 504, and a DLP chip 505. The lightsource 501 is configured to emit a color light to the DMD 503 throughthe optical member 504. More specifically, the light source 501 includescolored laser diodes. For example, the laser diodes include red laserdiode, blue laser diode, and green laser diode. At a predetermined timeinterval, a single laser diode is turn on while the other laser diodesare off, thereby emitting a single colored laser beam onto the DMD 503.The light source controller 502 provides control signal to the lightsource 501 to switch laser diodes on and off based on predeterminedfrequency and sequence. For example, the switching of laser diodes issimilar to the function of the color wheel shown in FIG. 5.

FIG. 6 is a simplified diagram illustrating a 3-chip DLP projectionsystem according to an embodiment of the present invention. This diagramis merely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As shown in FIG. 5, the3-chip DLP projection system includes a light source, optics, andmultiple DMDs, and a color wheel system. As shown, each of the DMDs isassociated with a specific color.

In various embodiment, the white light beam comprises a substantiallywhite laser beam provided by the light source. In one embodiment, theoutput from the light source is laser beam characterized by asubstantially white color. In one embodiment, the light source combineslight output from blue, green, and red laser diodes. For example, theblue, green, and red laser diode can be integrated into a single packageas described above. Other combinations are possible as well. Forexample, blue and green laser diodes share a single package while thered laser diode is packaged by itself. The blue laser diode can bepolar, semipolar, and non-polar. Similarly, green laser diode can bepolar, semipolar, and non-polar. For example, blue and/or green diodesare manufactured from bulk substrate containing gallium nitridematerial. For example, following combinations of laser diodes areprovided, but there could be others:

-   -   Blue polar+Green nonpolar+Red*AlInGaP    -   Blue polar+Green semipolar+Red*AlInGaP    -   Blue polar+Green polar+Red*AlInGaP    -   Blue semipolar+Green nonpolar+Red*AlInGaP    -   Blue semipolar+Green semipolar+Red*AlInGaP    -   Blue semipolar+Green polar+Red*AlInGaP    -   Blue nonpolar+Green nonpolar+Red*AlInGaP    -   Blue nonpolar+Green semipolar+Red*AlInGaP    -   Blue nonpolar+Green polar+Red*AlInGaP

In an alternative embodiment, the light source comprises a single laserdiode. For example, the light source comprises a blue laser diode thatoutputs blue laser beams. The light source also includes one or moreoptical members that change the blue color of the laser beam. Forexample, the one or more optical members include phosphor material.

It is to be appreciated that the light source may include laser diodesand/or LEDs. In one embodiment, the light source includes laser diodesin different colors. For example, the light source may additionallyinclude phosphor material for changing the light color emitted from thelaser diodes. In another embodiment, the light source includes one ormore colored LEDs. In yet another embodiment, light source includes bothlaser diodes and LEDs. For example, the light source may includephosphor material to change the light color for laser diodes and/orLEDs.

In various embodiments, laser diodes are utilized in 3D displayapplications. Typically, 3D display systems rely on the stereopsisprinciple, where stereoscopic technology uses a separate device for eachperson viewing the scene which provides a different image to theperson's left and right eyes. Examples of this technology includeanaglyph images and polarized glasses. FIG. 7 is a simplified diagramillustrating 3D display involving polarized images filtered by polarizedglasses. As shown, the left eye and the right eye perceive differentimages through the polarizing glasses.

The conventional polarizing glasses, which typically include circularpolarization glasses used by RealD Cinema™, have been widely accepted inmany theaters. Another type of image separation is provided byinterference filter technology. For example, special interferencefilters in the glasses and in the projector form the main item oftechnology and have given it this name. The filters divide the visiblecolor spectrum into six narrow bands—two in the red region, two in thegreen region, and two in the blue region (called R1, R2, G1, G2, B1 andB2 for the purposes of this description). The R1, G1 and B1 bands areused for one eye image, and R2, G2, B2 for the other eye. The human eyeis largely insensitive to such fine spectral differences so thistechnique is able to generate full-color 3D images with only slightcolour differences between the two eyes. Sometimes this technique isdescribed as a “super-anaglyph” because it is an advanced form ofspectral-multiplexing which is at the heart of the conventional anaglyphtechnique. In a specific example, the following set of wavelengths areused:

Left eye: Red 629 nm, Green 532 nm, Blue 446 nm

Right eye: Red 615 nm, Green 518 nm, Blue 432 nm

In various embodiments, the present invention provides a projectionsystem for projecting 3D images, wherein laser diodes are used toprovide basic RGB colors. FIG. 8 is a simplified diagram illustrating a3D projection system according to an embodiment of the presentinvention. This diagram is merely an example, which should not undulylimit the scope of the claims. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications. As shown inFIG. 8, a projection system includes a projector 801. The projector 801is configured to project images associated for one eye (e.g., left eye).The projector 801 includes a first light source. The first light sourceincluding a first set of laser diodes: a red laser diode, a green laserdiode, and a blue laser diode. Each of the laser diode is associatedwith a specific wavelength. For example, red laser diode is configuredto emit a laser beam characterized by a wavelength of 629 nm, greenlaser diode is configured to emit a laser beam characterized by awavelength of 532 nm, and blue laser diode is configured to emit a laserbeam characterized by a wavelength of 446 nm. It is to be appreciatedthat other wavelengths are possible as well.

In various embodiments, the blue laser diode is characterized by anon-polar or semi-polar orientation. For example, the blue laser diodeis fabricated from gallium nitride containing substrate. In one specificembodiment, the blue laser diode is manufactured from bulk substratematerial. Similarly, the green laser diode can manufactured from galliumnitride containing substrate as well. For example, the green laser diodeis characterized by a non-polar or semi-polar orientation.

It is to be appreciated that color LEDs may also be used to providecolored light for the projection elements. For example, a red LED can beused instead of a red laser diode in providing the red light. SimilarlyLED and/or laser diodes in various colors can be interchangeably used aslight sources. Phosphor material may be used to alter light color forlight emitted from LED and/or laser diodes.

The projector 802 is configured to project images associated for theother eye (e.g., right eye). The second light source including a secondset of laser diodes: a red laser diode, a green laser diode, and a bluelaser diode. Each of the laser diode is associated with a specificwavelength, and each of the wavelengths is different from that of thecorresponding laser diodes of the first light source. For example, thered laser diode is configured to emit a laser beam characterized by awavelength of 615 nm, the green laser diode is configured to emit alaser beam characterized by a wavelength of 518 nm, and the blue laserdiode is configured to emit a laser beam characterized by a wavelengthof 432 nm. It is to be appreciated that other wavelengths are possibleas well.

Projectors 801 and 802 shown in FIG. 8 are positioned far apart, but itis to be appreciated that the two projectors may be integrallypositioned within one housing unit. In addition to light sources andimage source, the projectors include optics for focusing images from thetwo projectors onto the same screen.

Depending on the specific application, various types of filters can beused to filter projected images for viewers. In one embodiment, bandpassfilters are used. For example, a bandpass filter only allows one set ofRGB color wavelength to pass to an eye. In another embodiment, notchfilters are used, where the notch filters would allow substantially allwavelength except a specific set of RGB color wavelength to pass to aneye. There can be other embodiments as well.

In certain embodiments, the present invention provides a liquid crystalon silicon (LCOS) projection system. FIG. 9 is a simplified diagramillustrating a LCOS projection system 900 according to an embodiment ofthe present invention. This diagram is merely an example, which shouldnot unduly limit the scope of the claims. One of ordinary skill in theart would recognize many variations, alternatives, and modifications. Asshown in FIG. 9, a green laser diode provides green laser light to thegreen LCOS through splitter 901; a blue laser diode provides blue laserlight to the blue LCOS through splitter 903; and a red laser diodeprovides red laser light to the red LCOS through splitter 904. Each ofthe LCOS is used to form images in a predetermined single color asprovided by its corresponding laser diode, and the single-colored imageis combined by the x-cube component 902. The combined color image isprojected onto the lens 906.

In various embodiments, one or more laser diodes used in the projectionsystem 900 are characterized by semi-polar or non-polar orientation. Inone embodiment, the laser diodes are manufactured from bulk substrate.In a specific embodiment, the blue and green laser diodes aremanufactured from gallium nitride containing substrate. It is to beappreciated that color LEDs may also be used to provide colored lightfor the projection elements. For example, a red LED can be used insteadof a red laser diode in providing the red light. Similarly LED and/orlaser diodes in various colors can be interchangeably used as lightsources. Phosphor material may be used to alter light color for lightemitted from LED and/or laser diodes.

The LCOS projection system 900 comprises three panels. In an alternativeembodiment, the present invention provides a projection system with asingle LCOS panel. Red, green, and blue laser diodes are aligned wherered, green, and blue laser beams are collimated onto a single LCOS. Thelaser diodes are pulse-modulated so that only one laser diode is powerat a given time and the LCOS is lit by a single color. It is to beappreciated that since colored laser diodes are used, LCOS projectionsystems according to the present invention do not need beam splitterthat split a single white light source into color beams as used inconventional LCOS projection systems. In various embodiments, one ormore laser diodes used in the single LCOS projection system arecharacterized by semi-polar or non-polar orientation. In one embodiment,the laser diodes are manufactured from bulk substrate. In a specificembodiment, the blue and green laser diodes are manufactured fromgallium nitride containing substrate. In various embodiments, theconfiguration illustrated in FIG. 9 is also used in ferroelectric liquidcrystal on silicon (FLCOS) systems. For example, the panels illustratedFIG. 9 can be FLCOS panels.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. Therefore, the above description and illustrations should not betaken as limiting the scope of the present invention which is defined bythe appended claims.

What is claimed is:
 1. A projection system comprising: an inputinterface for receiving one or more frames of images; a LCOS (LiquidCrystal on Silicon) chip; an edge emitting laser diode configured toemit laser light onto the LCOS chip, the edge emitting laser diode beingcharacterized by a non-polar or semi-polar orientation formed on agallium and nitrogen containing material; and a power sourceelectrically coupled to the edge emitting laser diode.
 2. The projectionsystem of claim 1 wherein the edge emitting laser diode is at least oneof a green laser diode, a blue laser diode, or a red laser diode, andwherein the edge emitting laser diode is configured on a mountingsurface.
 3. The projection system of claim 1 further comprising acondensing lens coupled to the edge emitting laser diode.
 4. Theprojection system of claim 1 further comprising a projection lenscoupled to the edge emitting laser diode and the LCOS chip.
 5. Theprojection system of claim 1 wherein the edge emitting laser diode isone of a red laser diode, a green laser diode, or a blue laser diode. 6.The projection system of claim 1 wherein the edge emitting laser diodeis characterized by a {20-21} orientation.
 7. The projection system ofclaim 1 wherein the edge emitting laser diode is a green laser diodecharacterized by a semi-polar orientation.
 8. The projection system ofclaim 1 wherein the edge emitting laser diode is a blue laser diodecharacterized by a semi-polar orientation.
 9. The projection system ofclaim 1 wherein the edge emitting laser diode is a blue laser diodecharacterized by a non-polar orientation.
 10. The projection system ofclaim 1 wherein the edge emitting laser diode is characterized by aspectral width of about 0.5 nm to 2 nm.
 11. The projection system ofclaim 1 wherein further comprising a dichroic filter coupled to the edgeemitting laser diode.
 12. A projection system comprising: an interfacefor receiving images or video signal; a LCOS (Liquid Crystal on Silicon)chip; an edge emitting laser diode configured to emit laser light ontothe LCOS chip, the edge emitting laser diode being operable in the490-540 nm wavelength range and characterized by a {20-21} semi-polarorientation, the edge emitting laser diode comprising a stripe regioncharacterized by a cavity orientation substantially in a projection of ac-direction; and a power source electrically coupled to the edgeemitting laser diode.
 13. A projection system comprising: an interfacefor receiving images or video signal; a LCOS (Liquid Crystal on Silicon)chip; an edge emitting laser diode formed on a gallium and nitrogencontaining material, the edge emitting laser diode configured to emitlaser light onto the LCOS chip, the edge emitting laser diode having awavelength of about 490 nm to 540 nm; and a power source electricallycoupled to the edge emitting laser diode.
 14. The projection system ofclaim 13 wherein the edge emitting laser diode is characterized by asemipolar {20-21} orientation.
 15. The projection system of claim 13wherein the edge emitting laser diode is characterized by a semipolar{20-21} orientation and comprises a stripe region characterized by acavity orientation substantially in a projection of a c-direction. 16.The projection system of claim 13 wherein the edge emitting laser diodeis characterized by a c-plane orientation.
 17. The projection system ofclaim 13 wherein the edge emitting laser diode is also operable in a430-480 nm wavelength range and is characterized by a c-planeorientation.
 18. The projection system of claim 13 wherein the edgeemitting laser diode is also operable in the 430-480 nm wavelength rangeand is characterized by a nonpolar or semipolar orientation.
 19. Theprojection system of claim 13 wherein the edge emitting laser diode iscomprised of GaAlInP material.
 20. The projection system of claim 13wherein edge emitting laser diode is characterized by a spectral widthof about 0.5 nm to 2 nm.